Air balanced oil well pumping system



Jan. 27, 1970 R. G. PEARSON AIR BALANCED OIL WELL PUMPING SYSTEM 2Sheets-Sheet 1 Filed March 4. 1968 W w.. w. .w am@ T5 m@ Jan. 27, 1970R. G. PEARsoN AIR BALANCED OIL WELL PUMPING SYSTEM 2 Sheets-Sheet 2Filed March 4. 1968 l Z'N vE/y roza j@ 055er @u PEQESoN BY mw/ T-roe/Ev.

United States Patent O 3,491,538 AIR BALANCED OIL WELL PUMPING SYSTEMRobert G. Pearson, Long Beach, Calif., assignor to Driltrol, Long Beach,Calif., a corporation of California Filed Mar. 4, 1968, Ser. No. 710,126Int. Cl. F1511 15/18; F04b 17/00 U.S. Cl. 60--52 16 Claims ABSTRACT OFTHE DISCLOSURE In the production of certain oil wells which do not havesufficient formation pressure to effect flowing of the well fluids tothe earths surface, it is the practice to employ artificial fluid lift.One common lift comprises a reciprocating pump adapted to be installedin the well and operable by a string of reciprocable sucker rods whichextend to the earths surface, the sucker rod string being caused toreciprocate by power means such as a walking beam, or, as in the case ofthe present invention, by a pump jack operable by hydraulic fluidpressure.

Various pump jack operating and control systems have been proposedheretofore, including the use of air or other gas, such as nitrogen orthe like, herein generically referred to as air, under pressure to applya force to the hydraulically operable pumping jack, whereby to at leastpartially balance the dead Weight of the sucker rod string and desirablya portion of the weight of the hydrostatlc column of well uid in thewell production pipe. Such systems, obviously, reduce the requiredhydraulic pressure applicable to the pump jack periodically to effectlifting of the sucker rod string.

Ordinarily, such systems are periodically or constantly supplied withair under pressure from an outside source, so as to maintain a desiredbalancing force on the system, and more particularly, on the pump jack.

An object of the present invention is to provide a well pumping systemof the air pressure loaded, hydraulically operated pump Ajack type whichis relatively simple to build, and, therefore, inexpensive, but which,at the same time, is durable, and therefore has long life expectancy.

Another object of the invention is to provide an air pressure loaded,hydraulically operated pump jack operating system that requires theapplication of small additional horsepower to a pump to effect flow ofthe hydraullc fluid and lifting of the sucker rod string.

Yet another object is to provide an air pressurized, hydraulicallyoperated pumping jack system, in which air is continuously supplied tothe hydraulic fluid reservoir from the hydraulic system itself duringoperation of the system, thereby eliminating the need for theapplication of air pressure to the system, either periodicallyorucontinuously from an outside source. More specifically, in accordancewith this objective, a low-speed compressor is employed to returnhydraulic fluid from a system drain to the pressurized reservoir, suchdrain fluid inherently having air entrained therein, whereby to maintainthe reservoir under the desired working or sucker rod counterbalancingpressure.

3,491,538 Patented Jan. 27, 1970 rice Still another object of theinvention is to provide an air pressure loaded, hydraulically actuated,pump jack operating system wherein a control valve is moved betweenfirst and second positions to cause flow of hydraulic fluid to the pumpjack and exhaust of hydraulic fluid from the pump jack, the controlvalve being controlled by a pilot valve which is responsive to fluidpressure when the pump jack reaches the end of its upstroke to causeshifting of the control valve to its second position, initiating,thereby, the downstroke of the pump jack.

A further object of the invention is to provide an air pressure loaded,hydraulically actuated, pump jack system in which a pump is employed tosupplement the hydraulic pressure and cause flow to effect upstroke ofthe pump jack, wherein pressure regulator means are provided to preventthe application of an inlet pressure on the pump in excess of the pumpoutlet pressure, when the pump jack commences its downstroke.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specification. It will nowbe described in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is a View diagra'mmatically illustrating an air pressureloaded, hydraulically operated, pump jack system in accordance with theinvention, the system being conditioned for upstroke of the pump jack;and

FIG. 2 is a view similar to FIG. 1, but showing the system conditionedfor downstroke of the pump jack.

In the system herein illustrated, it is desired that a pump jack P,comprising a fluid pressure operated actuator having a cylinder 1 and apiston 2 with rod 3, be operated to effect reciprocation of a string ofsucker rods (not shown) which extend downwardly into an oil well. Withinthe well, the sucker rod string would be connected to the plunger of areciprocating pump (not shown) t0 cause the ow of well uids upwardlythrough the well pipe 4 and into a flow line A5, from which the welliiuid Will ow to a suitable reservoir or tank, as is well known.

At its upper end, the sucker rod string would be con- I nected to areciprocable polish rod 6 which extends through the usual stuffing box7, and this polish rod is connected by a coupling 8 to the lower end ofthe piston rod 3. In order that the rod 6 may be reciprocated, thecylinder 1 has a conduit 10 for the admission and exhaust of hydraulicfluid under pressure below the piston 2, upon operation of theair-hydraulic system hereinafter to be described. At the upper end ofthe cylinder 1 is an outlet conduit 20, and at the lower end of thecylinder 1 is an outlet conduit 30. Outlet conduits 20 and 30 may berespectively provided with check valves 21 and 31, and each of theseoutlet conduits leads to a drain tank 40'. These conduits 20 and 30carry leakage to the drain tank 40 and prevent vacuum interference withthe operation of the pump jack in coniunction with check valves 21, 31.

As viewed in FIG. 1, the pump jack P is shown as upstroking, pressurefluid being supplied through conduit 10 below the piston 2. In order toeffect such upstroking of the pump jack P, the force derived from thepressure uid supplied through the conduit 10 must overcome the weight ofthe entire string of sucker rods, plus the weight of the column of uidin the well pipe 4, and obviously must overcome friction. Thus, thenecessary force may be substantial, as, for example, when the pumpoperated by the pump jack is located several thousands of feet down inthe earth. As will hereinafter be more fully described, the hydraulicfluid is pressurized to effect upstroke of the pump jack P by airpressure in a supply tank 50 and by supplemental pressure derived from apump 60. As previously indicated, the system may be pressurized by airso as to provide an upward force on the pump jack piston 2 equal to theweight of the entire sticker rod string, plus a desired portion of theweight of the column of well uid to be lifted.

Referring to the supply tank 50, it is preferably provided with a fillervalve 51, a shut-off Valve 52 adapted to allow filling of the tank tothe desired level, a working pop valve 53 and associated pressure gauge54, and a safety pop valve 55. A return conduit 56 is provided, and atthe lower end of the tank-is an outlet conduit 57 leading to a normally.open solenoid valve 58 which provides means for causing a ball valve 59in an outlet conduit 61 to remain open during operation of the system.This outlet conduit 61 will supply Huid fromthe tank 50, in a mannerhereinafter to be described, to the pump 60 and to the pump jack inletwhen the valve 59 is open.

In order to .open the valve 59, it is provided with an operator lever 62connected to the rod 63 of a 'differential area operated actuatorcylinder 64. Conduit 57 is connected to the lower portion of the tank 50and has a branch 57a leading to one side of the piston of actuatorcylinder 64, line 57 leading to the other side of the actuator pistonthrough the solenoid valve 58 when it is in one position. However, whenthe solenoid of valve 58 is energized, as seen in FIGS. l and 2, thevalve 58 closes olf conduit 57 and the larger end area of the actuatorpiston is exhausted to the drain tank 40 through a conduit 65.Therefore, the pressure of uid in the supply tank 50, acting on thesmaller effective area of the piston of the actuator cylinder 64, willcause the rod 63 to open the valve 59. Thus, energization of thesolenoid valve 58 conditions the system for operation.

Hydraulic fluid flowing from the tank 50 through conduit 61 followsthree courses: rst, via a branch conduit 61a to the inlet 66 of a pilotvalve means PV; secon-d, via a branch conduit 61b to a port 67 .of acontrol valve means CV; and a third, via a branch conduit 61e to theconduit 10 which leads into the pump jack cylinder 1.

In the illustrative embodiment, the pilot valve means PV is ahydraulically controlled, spring biased four-way valve which is adaptedto be shifted between a first position shown in FIG. 1 and a secondposition shown in FIG. 2, whereby to cause shifting of the control valvemeans CV between a first position shown in FIG. 1 and a second positionshown in FIG. 2. More specifically, the pilot valve PV includes anoutlet 70 communicating with a conduit 71, which leads to an end port 72of the control valve CV, and the pilot valve PV further includes a spool73 spring loaded to the above-mentioned first position so that ports 66and 70 are in communication, whereby pressure uid flows from the pilotvalve PV to the end port 72 of the control valve CV. This control valveCV has a spool 74 which is forced by pressure entering port 72 to theabove-mentioned rst position, so that the control valve port 67 is incommunication with a control valve port 75 leading to an inlet conduit76 connected to the inlet side of the aforementioned pump 60.

When the pilot Valve spool 73is in the first position of FIG. l, port70a thereof is in communication with an exhaust port 7.0b which leadsthrough an exhaust conduit 7 0c to a junction with the aforementionedconduit 65 leading to the drain tank 40. An end port 72a of the controlvalve CV communicates through a conduit 72b vwith the pilot valve port70a, whereby to exhaust this end ofthe control valve CV, so that thecontrol valve spool 74 is held in its first position by the pressure offiuid at port 72 at the other end of the spool 74.

The discharge side of the pump 60 is connected by a discharge conduit 77to the center inlet port 78 of the control valve CV, which, when thespool 74 is in the first position of FIG. 1, communicates with adischarge port 79 of the valve CV. A conduit 80a leads from the valveport 79 to the abovementioned conduit 10 through a pump inlet pressureregulator valve REG, hereinafter to be described.

Thus, when the spool 73 ,of pilot valve PV and the spol 74 of controlvalve CVare in ytheir rst positions, pressurized fluidis suppliedto thepump jack cylinder 1 via conduit 10 to cause the piston 2 to upstroke,lifting the polish rod 6 and attached string of pump sucker rods.

Various auxiliary valves and other equipment may be employed in thesystem as thus far described. For example, a metering valve VM'may beinstalled in the inlet conduit 61aleading to the center port 66 of the pilot valve PV, A filter F may be installe-d in the system, as, forexample, in the conduit 61C. A relief valve VR may be installed in thepump discharge conduit 77, such'relief valve having a conduit 77aleading back to the supply tank 50. The pump 60 ymay be driven by anelectric motor M and an electric circuit 60a to the motor M may includea low pressure shut-offl switch PS in pressure communication with thepump inlet conduit 76. A fluid level switch LS may also be in thecircuit 60a to the motor M and in pressure communication with the draintank 40 to shut off the motor if the fluid level in the drain tank risesabove a predetermined level, for example, due to excessive leakage inthe system.

The downstroke phase of operation .of the pump jack will be described inrelation to second positions of the spool 73 of the pilot valve PV andthe spool 74 of the control valve CV. A conduit leads from the upper endof pump jack cylinder 1 at a location at which, when the piston 2 is atany position below its uppermost position, the conduit 80 communicateswith the aforementioned conduit 20 which leads to the drain tank `40.This conduit 80 also communicates with an end port 81 of pilot valvePVso that the adjacent end of pilot valve spool 73 is exposed toatmosphere, thereby enabling the pilot valve spool 73 to assume andremain in its first position under the inuence of the valve spring 73a,thereby causing the spool 74 of control valve CV toassume and remain inits rst position under the influence of uid pressure at port 72, aspreviously described.

However, when the pump jack piston 2 reaches its uppermost position, itwill he seen in FIG. 2 that the conduit 80 will be in communication withthe pressure uid inlet conduit 10, but the conduit 20 will be shut offby piston 2. Thus, pressure fluid will ow through the pump jack cylinder1 to conduit 80 and to the end port 81 of pilot valve PV, causing aforce fwhich will move the valve spool 73 to the right or the secondposition shown in FIG. 2. At this time, port 72 of the control valve CVwill communicate through conduit 71 with pilot valve port 70, therebyexhausting the right hand end of the control valve CV to the drain tankthrough conduit 70C. In addition, the pilot valve inlet port 66communicates with port 70a, so that pressure uid from the supply tank 50flowing through conduit 61a will flow through the pilot valve PV to theend port 72a of control valve CV, whereby to forc the spool 74 to'itssecond position (FIG. 2).

At this second position of spool 74 of the control valve CV, its port 78and port 67 communicate so Athat the discharge side of the pump 60,namely, the conduit 77, is connected back to the supply tank 50; whilethe inlet side of the pump 60, namely, conduit 76, is connected to theconduit 10 through the regulator valve REG.

This regulator valve, as previously indicated, serves to prevent theapplication of an inlet pressure on the pump 60 which exceeds thedischarge pressure. In this Iconnection, it will be understood that whenthe pump jack' piston first commences its downstroke, following movementof the pilot and control'valve spools 73 and 74to their respectivesecond positions, and the pump jack cylinder 1 below the piston 2communicates with the pump inlet conduit 76, the pump inlet pressure isa function of the entire weight of the sucker rod string, plus theweight of the column of fluid in the well pipe 4, and the effectivecross-sectional area of the piston 2, forcing fluid into the pump inletconduit 76 as the entire Weight moves downwardly. On the other hand, thedischarge pressure of the pump60 is, as previously indicated, a'functionof the pressure of the air in the supply tank 50, which will be selectedso as to balance the Weight of the sucker rod string and a portion, sayone-half, ofthe weight of the Well fiuid column, Under thesecircumstances, the inlet pressure lat pump 60 may exceed the ldischargepressure an amount resulting from one-half the weight of the well fluidcolumn acting to force the piston 2l downwardly. This condition, as willbe understood in the art, is a momentary condition, since thereciprocating'pump plunger in the well vhas a travelling valve whichcloses on the upstroke of the plunger and opens responsive to downstrokeof the plunger. Thus, when the just-mentioned travelling valve opens,the weight of the well fluid columnwill be supported by the Well pumpstanding valve, and the inlet pressure on the pump K60 will be reduced.

In' any event, the regulator Valve REG reacts tothe ypresence of aninlet pressure greater than outlet pressure at pump 60 to adjust thepressure atthe pump inlet. Accordingly, while regulator means may beemployed either inthe pump inlet conduit 76`or in the pump dischargeconduit,'the valve REG, in the illustrative embodiment', is shown asbeing interposed between thecontrol valve CV and the pump dischargeconduit 77. This valve REGincludes a spool 90, an end ofthe valve havinga port 91 which is connected by a branch conduit 91a to the pumpdischarge conduit 77, so that pump discharge pressure is always appliedto oneend of the spool 90. The otherend ofthe valve REG has a .port 92which is connected by a conduit 92a to the control valve port,79 whichreceives pump discharge during -upstroke of the pump jack. Thus,

.during upstroke of ,the pumprjack, the discharge presfsure.- from thepump 60 is also applied to the regulator valve.spool90 through port. 92,as Well as port 91, and

the spool 90 is balanced., the pump discharge flow passing through vthefull open center ports 90C and 90d of the regulator valve RFGf, However,when the spool 74, of control valve CV is in its second position, theconduit 92a will be conducting fluid to port 79 from the pump jackvcylinder 1, and port 70 communicates with the inlet conduit 76 to pump60. Thus, the lcomparatively high pressure, at the regulator valve port92 will shift the regulator valve spool 90 tothe right, as seen in FIG.2, to reduce the iiow throughY the regulator valve` and thereby reducethe pressurey at the inlet to pump 60 during the initial downward travelvof thevk pump jack piston, until 1 y the well pump *travelling valveopens to reduce the weight aifectin g the inlet pressure at' pump 50.

f The downstroke ofthe pump jack will continue yuntil lthe piston 2passes a branch conduit 80e adjacent the lower end of the'fcylinder 1,at which time the pressure in lconduit 80 holding the pilot valve spool73 in its second position will be vented through a check valve 80h inbranch conductory 80e into the cylinder 1 above piston 2, a checkl valve80C being provided in the conduit 80 to y prevent such venting when thepiston 2 is above the branch means comprises a compressor 100 connectedby an intake conduit 101 to the drain tank 40 and having theaforementioned return conduit 56 leading to the supply tank 50 from thedischarge side of the compressor. Preferably, the compressor 100 is ofthe'rnultiple piston type driven by the motor M through a speed reducerat such a speed as to constantly scavenge the drain fluid from the draintank, along with air entrained in the fluid, and replenish the supplytank with compressed air and with the scavenged fluid. Preferably, thecompressor should operate at a speed which is more than adequate toscavenge the drain fluid, thus the pumping chambers of the compressorwill fill partially with drain fiuid and partially with air from theatmosphere. The speed of compressor 100 should also be such that tank 50is supplied with air in greater volume than is required to maintain thedesired balance pressure, excess air being relieved through the workingpop valve 53, or, in the event of failure of the valve 53, throughsafety pop valve 55.

The operation of the system as a Whole is believed to be clear from theforegoing, without further elaboration, and while specific details andarrangements of conduits and valve, as well as other components, havebeen herein shown and described, changes and alterations may be madewithout departing from the spirit of the invention.

I claim:

1. In a system for operating a pump jack having a cylinder and a pistonreciprocable in said cylinder for reciprocating a string of well pumpsucker rods: a supply tank for hydraulic pump jack operating fluid, saidtank having means enabling pressurizing the same with air, a drain tank,means including iiuid operated control means lfor conducting said fluidto said pump jack cylinder from said supply tank and for returning saidfluid from said pump jack cylinder cyclically, means for exhausting saidcontrol means to said drain tank, and a compressor connected to saiddrain tank and to said supply tank for returning iuid and compressed airfrom said drain tank to said supply tank to maintain the air pressure insaid supply tank.

2. A system as defined in claim 1; wherein said means for conductingsaid fluid includes a pump, control valve means interposed between thepump inlet and the pump discharge and movable between a irst position atwhich said pump discharge is connected to said cylinder and said pumpinlet is connected to said supply tank and a second position at whichsaid pump discharge is connected to said supply tank and said pump inletis connected to said cylinder, and means for moving said control valvemeans between said positions. 3. In a system for operating a pump jackhaving a cylinder and a piston reciprocable in said cylinder forreciprocating a stringof well pump sucker rods; a supply tank forhydraulic pump jack operating fluid, said tank having means enablingpressurizing the same with air, a drain tank, means including fluidoperated control means for conducting said -fluid to said pump jackcylinder from said supply tank and for returning said iiuid from saidpump jack cylinder cyclically, means for exhausting said control meansto said drain tank, and compressor means for returning fluid andcompressed air from said drain tank to said supply tank to maintain theair pressure in said supply tank, said means for conducting said uidincluding a pump, control valve means interposedbetween the pump inletand the pump discharge and movable between a first position at whichsaid pump discharge is connected to said cylinder andsaid vpump inlet isconnected to said supply tank and a second position at which said pumpdischarge is connected to said supply tank and said pump inlet isconnected to said cylinder, and means for moving said control Valvemeans between said positions, said .moving means including pressureregulator means for preventing a pressure at said pump inlet greaterthan pressure at said pump discharge when said valve means is in saidsecond position.

4. A system as defined in claim 1; wherein said means for conductingsaid fluid includes a pump, control valve means interposed between thepump inlet and the pump discharge and movable between a first positionat which said pump discharge is connected to said cylinder and said pumpinlet is connected to said supply tank and a second position at whichsaid pump discharge is connected to said supply tank and said pump inietis connected to said cylinder, and means for moving. said control valvemeans between said positions including pilot valve means connected tosaid cylinder and to said control valve means and responsive to movementof said pump jack piston to the end of its movements in oppositedirections to cause movement of said control valve means to said firstand second positions.

5. A system as defined in claim l; wherein said means for conductingsaid fluid includes a pump, control valve means interposed between thepump inlet and the pump discharge and movable between a first positionat which said pump discharge is connected to said cylinder and said pumpinlet is connected to said supply tank and a second position at whichsaid pump discharge is connected to said supply tank and said pump inletis connected to said cylinder, means for moving said control valve meansbetween said positions, a source of power for said pump, and drive meansconnected to said source of power for operating said compressor means.

6. Ina system for operating a purnp jack having a cylinder and a pistonreciprocable in said cylinder for reciprocating a string of well pumpsucker rods: a supply' tank for hydraulic pump jack operating fluid,said tank having means enabling pressurizing the same with air, a draintank, means including uid operated control means for conducting saidiiuid to said pump jack cylinder from said supply' tank and forreturning said fluid from said pump jack cylinder cyclically, means forexhausting said control means to said drain tank, and compressor meansfor returning fluid and compressed air from said drain tank to saidsupply tank to maintain the air pressure in said supply tank, said meansfor conducting said fluid including a pump, control valve meansinterposed between the pump inlet and the pump discharge and movablebetween a first position at which said pump discharge is connected tosaid cylinder and said pump inlet is connected to said supply tank and asecond position at which said pump discharge is connected to said supplytank and said pump inlet is connected to said cylinder, means for movingsaid control valve means between said positions, a source of power forsaid pump, drive means connected to said source of power for operatingsaid compressor means, said compressor means comprising a multiplepiston compressor, and said drive means including speed reducer meansfor driving said compressor at low speed relative to said pump.

In an oil well pumping system for connection to a string of reciprocablepump sucker rods: a pump jack having a vertically disposed cylinder, apiston and rod reciprocable in said cylinder and connectible to saidstring of pump rods, an inlet and outlet conduit below said piston,means for cyclically supplying pressure fluid to said cylinder andexhausting said fluid from said cylinder through said conduit to effectupstroking and downstroking of said piston and rod, said means includinga fluid supply tank having air therein for applying a load balancingforce to said fluid during upstroking of said piston and r'od, pumpmeans having an inlet and a discharge, valve means movable between afirst position connecting said pump means discharge to said conduit andsaid pump means inlet to said supply tank and a second positionconnecting said conduit to said pump means inlet and said pump meansdischarge to said supply tank, means for moving said valve means to saidfirst position when said piston and said rod reach the end of saiddownstroke and for moving said valve means to said second position whensaid piston and rod reach the end of said upstroke, and pressureregulator means for preventing the application of pressure at said pumpmeans inlet in excess of the pressure at said pump means discharge whensaid valve means is in said second position.

8. A pumping system as defined in claim 7; wherein said pressureregulator means includes a pres-sure operated regulator valve interposedbetween said pump means inlet and said pump means discharge. ,i

9. A pumping system as defined in claim 7; wherein said pressureregulator means includes a pressure operated regulator valve interposedbetween said pump means inlet and said pump means discharge, saidregulator valve having a spool, a conduit connecting said regulatorvalve to said pump means discharge to subject one end of said spool tothe 4pressure at said pump means discharge, another conduit connectingsaid regulator valve to said valve means to subject the other end ofsaid spool to fluid pressure, and said valve means including means foradmitting the pressure of fluid from Said pump means discharge to saidanother conduit when said valve means is in said first position and foradmitting the pressure of fluid from said pump means inlet to saidanother conduit when said valve means is in said second position.

10. A pumping system as defined in claim 7; `Jvherein the means formoving said valve means to said first and second positions includespilot valve means movable to a first position for causing saidfirst-mentioned valve means to move to said first position, said pilotvalve means being movable to a second position to cause saidfirst-mentioned valve means to move to said second position, and meansfor moving said pilot valve means to said first and second positionswhen said piston and rod reach the end of their downstroke and upstroke.

11. A pumping system as defined in claim 7; wherein the means for movingsaid valve means to said first and second positions includes pilot valvemeans including a spool movable to a first position for causing saidfirstmentioned valve means to move to said first position, said pilotvalve means spool being movable to a second position to cause saidfirst-mentioned valve means to move to said second position, and meansfor moving said pilot valve means spool to said first and secondpositions when said piston and rod reach the end of their downstroke andupstroke including conduit means connecting said pump jack cylinder tosaid pilot valve means to cause movement of said spool to said first andsecond positions when said piston and rod reach the end of theirdownstroke and upstroke.

12. In a well pumping system for connection to a string of reciprocablepump rods: a pump jack having a vertically disposed cylinder, a pistonand rod reciprocable in said cylinder and connectible to said string ofpump rods, a supply tank for air pressurized fluid, conduit meansleading from said tank to said cylinder beneath said piston, pump meansin said conduit means, control valve means in said conduit means foralternately reversing the flow between said tank and said cylinder uponreversal of said control valve means, pilot valve means in said conduitmeans for reversing said control valve means, said pilot valve meanshaving fluid pressure responsive means for operating the same uponmovement of said piston to an upper position and to a 1iower position, apilot conduit leading to said pilot valve means and communicating withsaid cylinder below said piston when said piston reaches its upperposition and above said piston when said piston reaches its lowerposition to conduct uid pressure to said fluid pressure responsivemeans, a drain tank, an exhaust conduit leading from said pilot valvemeans to said drain tank, a compressor connected to said drain tank, anda conduit leading from said compressor to said supply tank forconducting compressed air and fluid from said drain tank to said supplytank.

13. A well pumping system as defined in claim 12; wherein said controlvalve means is fluid pressure operated, and including pilot conduitmeans connecting said control valve means to said pilot valve means,said pilot valve means having means for exhausting said pilot conduitmeans to said drain through said exhaust conduit upon reversal of saidcontrol valve means.

14. A well pumping system as defined in claim 12; wherein pressureregulator means are provided for preventing the application of an inletpressure on said pump means in excess of the discharge pressure of saidpump means when said control valve means reverses at the end of theupward movement of said piston.

15. A Well pumping system as dened in claim 12; wherein said supply tankis provided with pop valve means for limiting air pressure in saidsupply tank in response to operation of said compressor.

16. A well pumping system as defined in claim 12; wherein shut-olf valvemeans are provided in said conduit means leading from said supply tankto said cylinder, said shut-Off valve means including an actuatorcylinder, an actuator piston in said actuator cylinder having a rodprojecting from said actuator cylinder and connected to said shut-offvalve means to open and close the same upon shifting of said actuatorpiston, conduit means leading from said supply tank to said actuatorcylinder at oppo- References Cited UNITED STATES PATENTS 2,470,252 5/1949 Kyle. 2,481,623 9/ 1949 Rued. 2,489,412 11/1949 Harvey. 2,665,5511/ 1954 Chenault. 2,729,942 1/1956 Billings et al. 2,780,063 2/1957Bacchi.

EDGAR W. GEOGHEGAN, Primary Examiner U.S. Cl. X.R. 103-45

